Electrochemical Sensors

Arthur Gildea

ABC’s of Electrochemistry

1/26/2012

2 Center for Electrochemical Engineering Research, Ohio University

Overview

• Introduction

• Reference electrode

• Biosensors and Immunosensors

• Potentiometric sensor

• Amperometric sesnor

• Conductometric sensor

• Electrochemical Sensors in CEER Lab

• Conclusion

3 Ohio University - Avionics Engineering Center

Introduction

4

Introduction

• Electrochemical sensors are the largest and oldest

group of chemical sensors[1]

• With the oldest sensor dating back to 1950s, which

was used for oxygen monitoring[2]

• Miniaturized electrochemical sensors that could

measure a multitude of different chemical species

have been industrially available since mid-1980s[2]

• Currently electrochemical sensors account for

approximately 58% of all chemical sensors[3]

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History

5

Introduction

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[4]

6

Introduction

• Electrochemical sensors are electrochemical cell

which employs a two or three electrode arrangement

• Measurements by electrochemical sensor can be

taken at steady-state or transient conditions[5]

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Cell Design

7

Introduction

• In a two electrode system, there is a working and a

reference electrode, while three cell system has a work,

counter, and reference electrode

• The working electrode is the electrode where the chemical

reaction of interest is taking place

• The counter electrode or auxiliary electrode allows current

to flow between it and the working electrode without

effecting the system

• The reference electrode remains at a constant potential,

which allows it to behave independently of the working

electrode or the solution being measured while maintaining

a constant potential

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Cell Design

8

Introduction

• Physical size, shape, geometry,

selection of electrode material, and

construction of electrochemical

sensor depends on intended use[2]

• Cell design effects performance

parameters of the electrochemical

sensor

• Examples of performance

parameters are sensitivity, selectivity,

working range, and limit of detection

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Cell Design

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Reference Electrode

10

Reference Electrodes

• Standard hydrogen electrode

(SHE)

• Static mercury drop electrode

(SMDE)

• Saturated calomel electrode (SCE)

• Mercury/mercury oxide electrode

• Silver/Silver chloride electrode

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Common Reference Electrodes

11

Reference Electrodes

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Current Research into Integrated Reference Electrodes

• Miniaturize reference electrode (Ag/AgCl electrodes)

• Hybrid electrodes that can working in acidic and

alkaline solution

– Ex: silver tetramethylbis (benimidazolium) diiodide[6]

• Making disposable reference electrodes through

techniques like screen printing

• Microfluidic electrochemical sensors

• Solid-state reference electrodes that do not require

liquid junction

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Biosensors and Immunosensors

13

Biosensors

• Biosensors utilize immobilized

enzymes on an electrode surface

• They allow for very selective

chemical reactions to be measured

electrochemically

• Biosensor can measure a variety of

different chemical species, such as

glucose, lactate, and urea

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Introduction

14

Immunosensors

• Immunosensors transduce antigen-antibody

interactions directly into electrical signals[7]

• Have become vital in determining biochemical

targets relating to health concerns such as cancer[6]

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15

Biosensors

• Use of nano structures to immobilize enzymes, which

allows electrodes to have high catalytic activity and

high surface area (ex: graphene nano sheets)

• Protective film membranes, which allow extended life

time, better selectivity, and sensitivity (ex: Nafion)

• New techniques which allow better immobilization of

enzymes on nano structures, using other nano

structures and ionic liquids

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Current Research[6]

16

Immunosensors

• Carbon nanotubes are being used to immobilize

antigen, which protects and stabilizes species

• Cancer detection has been a driving force behind

much of the research due to inherent specificity and

accuracy of immunosensors

• Sandwich type sensors, which utilize immobilized

antibodies to attach antigens to solid surface, while a

second antibody carries a detection system, which is

usually an enzyme

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Current Research[6]

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Potentiometric Sensors

18

Potentiometric Sensors

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Introduction

• Potentiometric sensor apply a

current and measure the

potential response

• Linear response used for

calibration curve is given by

the Nernst equation

• One of the most commonly

used electrochemical sensors,

which is the pH meter

19

• Ion selective electrode developments, which has

allowed the measurement of minute amounts of

ionic species (ex: multiwalled carbon nanotube

membranes)

• Use of room temperature ionic liquids, instead of

paraffin, which greatly increases sensor

performance

• PVC membranes used as anion selective

membrane

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Potentiometric Sensors

Current Research[6]

20 Ohio University - Avionics Engineering Center

Amperometric Sensors

21

Amperometric Sensors

• Amperometric sensors apply a fixed

potential and measure the current

response, which is then related to

analyte concentration[5,6]

• Charge and mass transfer at the

working electrode surface directly

affects the current response,

therefore sensors must either be

charge or mass transfer controlled

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Introduction

22

Amperometric Sensors

• Improvements in nonenzyme based glucose and

hydrogen peroxide sensors

• Use of novel new materials, such as nonamaterials

and composite materials

• Screen printed microelectrode arrays, which allow

for low cost disposable sensors

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Current Research[6]

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Conductmetric Sensors

24

Conductometric Sensors

• Conductometric sensors measures the conductivity

change of the system in the presence of a give

solute concentration[5]

• The measure of the conductivity of an electrolyte is

often difficult due to polarization of the electrode at

the operating potential[5]

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Introduction

25

Electrochemical Sensors in CEER Lab

• Conductiviy meter (Mettler Toledo)

• Ammonia sensor (Thermo Electron Corporation)

• pH meter (Oakton, Hanna Instruments)

• Urea sensor (Developed by CEER)

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26

Conclusion

• Oldest and largest branch of chemical sensors

• Wide range of industrial and research application

• Designs of sensors are dependant on what is being

monitored by the sensor

• Wide range of new research in order to solve

inherent problems of different systems

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27 Center for Electrochemical Engineering Research, Ohio University

References

1. Janata, Jiri. Principles of Chemical Sensors. New York: Plenum, 1989. Print.

2. "Electrochemical Sensors." International Sensor Technologies. Web. 25 Jan. 2012.

<www.intlsensor.com/pdf/electrochemical.pdf>.

3. Janata, Jiri. "ELECTROCHEMICAL SENSORS." Electrochemistry Encyclopedia. Sept. 2010.

Web. 24 Jan. 2012. <http://electrochem.cwru.edu/encycl/art-s02-sensor.htm>.

4. Gushikem, Yoshitaka, and Simone S. Rosatto. "Metal Oxide Thin Films Grafted on Silica Gel

Surfaces: Recent Advances on the Analytical Application of These Materials." Journal of the

Brazilian Chemical Society 12.6 (2001). Print.

5. Liu, Chung-Chiun. "Electrochemical Sensors." CRC LLC, 2000. Print.

6. Kimmel, Danielle W., Gabriel LeBlanc, Mika E. Meschievitz, and David E. Cliffel.

"Electrochemical Sensors and Biosensors." Analytical Chemistry (2011): Print.

7. Tiefenauer, L., and C. Padeste. "Immunosensor." Laboratory for Micro- and Nanotechnology.

Paul Scherrer Institut, 23 July 2007. Web. 25 Jan. 2012.

<http://lmn.web.psi.ch/molnano/immuno.htm>.

www.ohio.edu/ceer

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contact:

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